1. Field of the Invention
The present invention relates to a semiconductor memory device.
2. Description of the Related Art
A dynamic random access memory (DRAM) is a semiconductor memory device capable of holding data for one bit with the use of one transistor and one capacitor. In the DRAM, the area per unit memory cell is small, integration for making a module is easy, and manufacturing cost is low.
In the DRAM, charge accumulated in the capacitor leaks due to off-state current of the transistor; therefore, there has been a need for recharging (refreshing) before necessary charge is lost.